package cn.dm.example.count;

import cn.dm.annoations.NotThreadSafe;
import lombok.extern.slf4j.Slf4j;

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;
import java.util.concurrent.Semaphore;

@Slf4j
@NotThreadSafe
public class CountExample1 {

    // 请求总数
    public static int clientTotal = 5000;

    // 同时并发执行的线程数
    // public static int threadTotal = 1; // 单线程运行结果均为5000
    public static int threadTotal = 200;

    public static int count = 0;

    public static void main(String[] args) throws Exception {
        ExecutorService executorService = Executors.newCachedThreadPool();
        final Semaphore semaphore = new Semaphore(threadTotal);
        final CountDownLatch countDownLatch = new CountDownLatch(clientTotal);
        for (int i = 0; i < clientTotal; i++) {
            executorService.execute(() -> {
                try {
                    semaphore.acquire();
                    add();
                    semaphore.release();
                } catch (Exception e) {
                    log.error("exception", e);
                }
                countDownLatch.countDown();
            });
        }
        countDownLatch.await();
        executorService.shutdown();
        log.info("count:{}", count);
        /**
         * 结果如下
         * 15:11:22.619 [main] INFO cn.dm.example.count.CountExample1 - count:4986
         * 15:12:04.673 [main] INFO cn.dm.example.count.CountExample1 - count:4994
         * 15:12:19.047 [main] INFO cn.dm.example.count.CountExample1 - count:4985
         * 15:12:35.454 [main] INFO cn.dm.example.count.CountExample1 - count:4975
         * 15:12:47.680 [main] INFO cn.dm.example.count.CountExample1 - count:4988
         *
         * 综上可以看出,运行多次均不到5000
         */
    }

    private static void add() {
        count++;
    }
}
